I had always read that is was Keith Moon that said that not John.
I had to check into that one for my own curiosity : Both Moon and Entwistle were present at the time, along with Richard Cole. in Zep bio 'Hammer of the Gods" , the phrase is attributed to John (the 3 were hanging out at a club partying, so who really knows) Actually, I had the phrase wrong, it was "we'll call it lead zeppelin, because it'll f*ing go over like a lead balloon"as he was referring to an imaginary band of Moon, Entwistle, Page , and Steve Winwood that never happened. Cole relayed the idea for the name to Jimmy and he saved it until the legendary foursome was unleashed on the world.
boy, I really boogered up John's last name in that post , huh !